Refined Estimates of Near-Field Radiated Seismic Energy Based on Integrated Surface and Underground Observations in Coal Mines

Accurate determination of the radiated energy from small earthquakes is critical for understanding the physical processes and energy partitioning of the source, as well as for assessing seismic hazards. However, precise estimates of radiated energy from small near-field earthquakes are limited by strong high-frequency attenuation near the surface, station availability, and difficulties related to path and site effect corrections. In this study, active-source seismic experiments were performed in five coal mines to develop a radiated seismic energy estimation method suitable for near-field mining settings (i.e., epicentral distances of 0.5–5 km). Through integrated surface and borehole observations, as well as high-quality waveform datasets at different blasting scales, explosive quantities, and network configurations were obtained. An improved Levenberg–Marquardt algorithm was used to invert the frequency-dependent geometric spreading exponent and inelastic attenuation parameters (Q₀) for each mining area. The surface Q₀ values were generally higher than those obtained from the borehole observations, reflecting differing observed frequency bands and propagating wavefield compositions. Horizontal-to-vertical spectral ratio methods were combined for site-effect correction, and the radiated seismic energies of individual events were then calculated and converted into energy magnitudes. The average energy magnitudes derived from multiple borehole stations agreed with the theoretical reference range; however, the surface multi-station average magnitudes were systematically underestimated. After establishing and applying the linear correction model, the surface-based results were consistent with the theoretical reference range. The coefficients of determination for the fits between radiated seismic energy and local magnitude and explosive quantity confirmed the reliability of the results. The method proposed in this study provides an effective technical approach for improved near-field estimates of radiated energy from small earthquakes and can be applied to microseismic monitoring in mines, active-source imaging, and earthquake source physics.